Configure the OSPF priority for the port during the election process for the designated router. The port with the highest priority number is the best candidate for the designated router. If you configure the priority to 0, the port cannot become either the designated router or a backup designated router.
default ip ospf priority
ip ospf port {slot/port[/sub-port][-slot/port[/sub-port]][,...]} priority <0-255>
ip ospf priority <0-255>
Identifies the slot and port in one of the following formats: a single slot and port (slot/port), a range of slots and ports (slot/port-slot/port), or a series of slots and ports (slot/port,slot/port,slot/port). If the platform supports channelization and the port is channelized, you must also specify the sub-port in the format slot/port/sub-port.
The default is 1.
GigabitEthernet Interface Configuration